Kye Whyte, Great Britain’s Olympic silver medallist from Tokyo, was stretchered off the course following a heavy crash in the BMX racing semi-finals.
Whyte, 24, lost control of his bike after the first jump and veered off course heading into the second ramp before crashing to the ground.
He was seen to immediately by medics while lying on the ground before he was lifted onto a stretcher and carried from the course.
Pictures showed he was receiving oxygen as he lay on the stretcher.
He will not advance to the final after the crash.
Whyte carried a back injury into the semi-finals and struggled through the quarter-finals on Thursday.
He said he would be “fighting on” but finished fifth in his first heat and made a slow start out of the gate in the second.
There did not appear to be contact with another rider before he lost control of his BMX.
Great Britain’s Beth Shriever is meanwhile bidding to defend her gold medal in the women’s race.
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